Topic 9 - Nuclear Fission and Fusion

What fuel is used in a nuclear power station?

Uranium-235

Why is uranium-235 used in a nuclear power station?

It undergoes nuclear fusion.

What is nuclear fission?

The splitting of a heavy element into two lighter ones.

Why is nuclear fission and fusion useful?

The reactions release lots of energy.

What causes a uranium atom to split in a power station?

A slow moving neutron.

Why do spent nuclear rods need to be stored for a long time?

They have a very long half life.

How is a a chain reaction sustained in a nuclear reactor?

Every fission reaction produces more neutrons that can go on and cause further fission reactions.

What happens if the chain reaction is not controlled?

The reactor can explode like a nuclear bomb.

How are people protected from the nuclear radiation in the reactor?

The reactor is surrounded by a thick concrete shield.

How is the energy produced from a fission reaction to create electricity?

The heat generated turns water into steam, the steam turns a turbine and a generator making electricity.

How is a chain reaction controlled?

Controlled rods.

What are control rods usually made of?

Boron

How do control rods prevent an uncontrollable chain reaction?

They absorb the neutrons so that they can’t cause further fission reactions.

How can control rods be used to control the rate at which energy is produced in a reactor?

Lowering the rods further into the reactor causes more neutrons to be absorbed and less energy is produced, raising them will do the opposite.

What substance is usually used as a moderator in the reactor?

Water.

What is the purpose of a moderator in the reactor?

To slow down the fast-moving neutrons that are produced so that they are more likely to cause further fission reactions.

What is fusion?

The joining of smaller elements to make heavier ones.

Where does fusion naturally occur?

The sun/stars.

What elements are involved in fusion in the Sun?

Hydrogen fuses into helium.

Why is fusion so difficult to sustain?

It requires extremely high temperatures in order to get the protons in hydrogen atoms to fuse together.

What two isotopes of hydrogen are used in fusion?

Deuterium (H-2), and Tritium (H-3)

What are the problems of containment with fusion?

The high temperatures will melt most materials on Earth.

How is fusion contained?

High magnetic fields are used to keep the hydrogen atoms away from the walls of the container.

Why does the fusion reactor need to be shielded in concrete?

The fusion reaction produces huge numbers of neutrons that can interact with materials and make them radioactive. Concrete is needed to prevent radiation escaping.

What are the advantages of fusion over fission?

Fusion produces more energy per reaction, it doesn’t produce radioactive waste.

What are the advantages of fission over fusion?

It doesn’t require high temperatures so it is easier to sustain for long periods and easier to contain.